Chocolate poisoning in dogs.
Dogs are susceptible to chocolate poisoning.  This is because they are more sensitive to the poisonous ingredient (theobromide), they are relatively small compared to humans, and they can very quickly eat a lot of chocolate (or whatever else they can get hold of!)
Charateristics that make poisoning more likely:
Small dogs have a lower body weight which makes them more susceptible.
Type of chocolate: Bakers chocolate, dark chocolates and cocoa powder/beans/shell mulches contain far more theobromide than the refined chocolates (milk and white chocolates).
Symptoms:
Gastrointestinal symptoms are common (vomiting, nausea, diarrhoea), as is increased drinking and urinating.
Later, or if large amounts are eaten, symptoms may include muscle tremors, seizures, irregular heartbeats, internal bleeding and possible heart failure.
How much is too much:
This is not always easy to answer, but one or a few milk/white chocolates are unlikely to cause any problems in healthy dogs.
With a dark or bitter chocolate however, as little as 25g can cause symptoms in a 20kg dog.
Symptoms normally start within 2 hours, but can take up to 24 hours.
If in doubt, rather take a cautious approach early on and contact us for advice.
Prompt treatment is essential in overdose cases.  We do provide 24-hour emergency cover for our clients, so even if you have a chocolate guzzling monster late at night – please call.
Symptoms can continue for up to 3 days.
Treatment:
By far the best treatment is to medically cause vomiting (ideally within half an hour of ingestion, but up to 2 hours, or even a little longer will reduce the amount of theobromide absorbed).
This is best done at the practice with an injectable drug that causes vomiting, reliably.
Lethal dosages and the numbers:
The lethal dose of theobromide is 100-500mg/kg of body weight.
Cocoa powder (20mg/g) and plain dark chocolate (15mg/g) contain the highest levels of theobromide.  Milk chocolate has around 2mg/g and white chocolate very little at 0.1mg/g).
Therefore, 100g of dark chocolate (1500mg theobromide) could kill a 10kg dog (1000mg potential lethal dose).
To get the same amount of theobromide from white chocolate this dog would need to eat 15kg of chocolate!
Put another way treatment is needed if your dog eats more than:
Ø  9g/kg of milk chocolate (the light brown one)
Ø  1.25g/kg of dark chocolate (dark brown/cooking chocolate)
Please note: these figures are not absolutes, please call for advice.